"This week" -- breaking news. Crisis in Iraq. Extremist fighters, now minutes from the capital, will we be drawn nto war? Plus, the surprising threat to the U.S. This morning Martha Raddatz on the ground in Baghdad. Then, political shocker. We came up short. Voters venting their anger. One of Washington's most powerful leaders ousted. This morning, Eric Cantor here live. And border crisis. They're not going to survive. Children flooding into the U.S. Without their parents, what can be done to prevent catastrophe. "This week" with George stephanopoulos begins now. Good morning, I'm Martha Raddatz coming to you from Baghdad. Where we're tracking breaking news in a fast-moving crisis that could draw the U.S. Back into war. President Obama now considering air strikes, as an army of jihadists remain just 60 miles of this capital, and while there will be no American boots on the ground, just last night, the aircraft carrier, "Uss George H.W. Bush," and two other warships were moved to the persian gulf. We have team coverage of every angle. But we begin here in Baghdad, where we arrived this morning to find a city bracing for attack. Ready to take up arms. A city where Americans gave their lives, now on the brink of civil war. Security forces here mobilizing. Residents here, hoarding food and supplies, fearing the extremists will strike. The country's political and religious leaders now calling for new recruits to take up arms. This morning, we met some of the young men eager to join the fight. Are you ready to take up arms? Definitely. Reporter: New recruits, mostly majority shias from the south of the country, pushing back against the extremist jihadist group threatening to drawing Iraq into a civil war. Exactly the nightmare scenario the U.S. Ambassador to Iraq told us he was deeply concerned about when we were in Baghdad earlier this year. The violence has a grinding effect and it can enflame these tensions that are there. Especially sectarian ones. Reporter: Emerging from the chaos in Syria, the extremists call themselves Isis for the islamic state of Iraq and Syria. Where they hope to build the new state under strict islamic rule. Their tactics so brutal, that even Al Qaeda has disavowed them. And as their fighters under black flags have marched south through Iraq, the cities have fallen one by one. From mosul in the north to tikrit. Where Isis claimed they executed some 6700. Their March causing an exodus of refugees throughout the country. I have traveled to Iraq more than 20 times in the past decade of war. Watching, as the U.S. Made standing up Iraqi security forces its primary mission. Back in 2005, a confident general David petraeus explained the goal for training Iraq's military. We have to make sure they're going to back up the other element. I think you saw that here today. Reporter: But those forces have largely failed. Abandoning their uniforms and billions of dollars of u.s.-provided weapons and equipment, now in the hands of the enemy. The U.S. Is now weighing how to respond to the deteriorating situation. President Obama moving warships into the persian gulf, including a carrier armed with missiles and packed with fighters jets. But on Friday, president Obama ruled out American forces returning to the country. We will not be sending U.S. Troops back into combat in Iraq. Ultimately it's up to the Iraqis as a sovereign nation to solve their problems.

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